help with solar fan

FlamingArrow · June 2021

Hi everyone. Thanks in advance for helping a newbie! I'm trying to get a fan hooked up in my greenhouse.
I got a 12V radiator fan, specs say it has a 6.6amp draw. I have a 150W/20A solar panel installed.
Summary of trials:
Panel -> charge controller -> battery -> thermostat -> fan = works but drains battery
Panel -> voltage regulator -> fan = fan clicks, doesn't start
Panel -> thermostat -> fan = fan clicks, doesn't start

Details:
I tried hooking the panel up to a voltage regulator to keep voltage around 14V but when hooked up the fan just clicks like it's trying to start, but won't. I turned up the amperage to max and the voltage above 16V on the regulator and same thing. So I hooked up a charge controller and old car battery to control the fan, and that works great but it drains my battery in half a day, so not the best option.
The fan is wired through a thermostat so it only runs over 85 deg to try to save the battery, but it still needs to run for 7+hrs/day and runs the battery to 9V before the end of the day.
Curious if anyone knows why the fan might be jumping/clicking but not starting when going directly to the panel through the thermostat, with or without the voltage regulator. If I go directly to the panel the fan works but doesn't seem as strong as going through the battery.

Photowhit · June 2021

How solar works, is a very long book, but several things should help;

FlamingArrow said:

I have a 150W/20A solar panel installed.

Something isn't correct here, if you had a 150 watt 20 amp solar panel it would only produce 150 watts

÷

20 amps = 6.5 volts.

More likely you have something like a 18 volt VMP solar panel producing 150

÷

18 volts = 8.33 amps during Standard Test Conditions (STC)

Unfortunately in the real world STC conditions rarely happen and solar panels heat up. When hot they tend to produce about 75% of STC (this is called NOCT values Normal Operating Cell Temperature) So produce around 120 watts.
________________________________

When charging a lead acid battery there is a 10-20% lose as the voltage regulator/ Charge Controller, maintains a voltage high enough for the transfer of current to the battery, You noted 14 volts for a 12 volt nominal battery or about 10-12% loss over the resting voltage of the battery.

If you are using an inexpensive PWM charge controller, you may be losing another 10 % or so.
______________________________________

Motors take a bit more energy to start than run. I suspect if you put the panel out in direct sunlight perpendicular to the sun, and give it a little push it would start and run. It would likely be slightly underpowered, but about right, it just needs the 'extra wattage to start that it can draw when connected directly to the battery. This extra energy can be 3-4x the running wattage and even higher....

----------------------------------------------------------------

In the end you will need more wattage to run the fan all day, You didn't say how large your battery was (amphours) but you will likely always be behind. Double the array (2 panels) should get you going without losing the energy from the battery.

You could also look for a less powerful, more efficient fan.

O2Cool makes a nice fan, most have been switched to 9 volt now, but you may find a used one on Facebook MarketPlace or Craigslist. Other efficient fans are likely around.

This one still says it uses 8 D cells which would make it a 12 volt, but likely has changed to 9 volt;

https://www.amazon.com/O2COOL-10-Inch-Portable-Charging-Pivoting/dp/B014CLAL8S/ref=asc_df_B014CLAL8S/

Photowhit · June 2021

Inexpensive 9 volt version you could run off a wall wart and AC adapter;
https://www.walmart.com/ip/Treva-10-inch-Battery-Powered-Portable-2-Speed-Table-Fan-with-Adapter-Black/24017579

littleharbor2 · June 2021

The 12 volt versions have a 12 volt aux power input port also. Great little fans.

FlamingArrow · June 2021

Sorry, my mistake. Amazon pulled up the wrong panel when I clicked on the link to the product in my orders. Apparently the one I purchased is no longer available and I can't find the specs on it. All it says on the description title is 150W 12V.
I played with it more this morning. The battery is only half charged right now, reading 6V. If I hook up the fan directly to it, it runs and pulls 6.6amps as expected. The solar panel was reading 17V, when the fan was hooked to it, it did not run at all. The meter said it was pulling 0.5a.
So a 150W panel is not enough to run this fan? Electronics has never been my strong point. I've taken a class but it was not explained well. I'm a pretty math/science oriented person so this has always frustrated me. Maybe I'll try another class. It is something I would love to have a better grasp on. Thanks again for taking the time to help me. I know how annoying newbies can be!

Unfortunately the little fans linked will not be powerful enough to help cool my greenhouse. The greenhouse is roughly 12'x28'. I have 2 box fans on a thermostat to push air in and I need a fan on the other end to pull it out.

littleharbor2 · June 2021

I have a pair of 12 volt radiator fans installed in my garage roof. They're hardwired to a 65 watt 12 volt solar panel. as long as the sun shines they operate. the stronger the sun hitting the panel, the faster the fans spin. Couldn't be simpler.

Photowhit · June 2021

FlamingArrow said:

I can't find the specs on it. All it says on the description title is 150W 12V.FlamingArrow said:

Most solar panels will have specs on the back of them. If not we could try to look them up if you have the name brand, should be in your amazon history.

FlamingArrow said:

The battery is only half charged right now, reading 6V.

6 volts is NOT half full, it's dead! Please don't hook anything up to it until it is fully charged, if it will take a charge.

We still don't know the size of type of battery, but rough idea of State of Charge for a 12 volt lead acid battery is;

Calculate battery state of charge percentage - Electrical Engineering Stack Exchange

Calculate battery state of charge percentage - Electrical Engineering Stack Exchange

FlamingArrow said:

The solar panel was reading 17V, when the fan was hooked to it, it did not run at all. The meter said it was pulling 0.5a.
So a 150W panel is not enough to run this fan?

Did you read as I explained why the fan wasn't running? How higher start up power is required? Did you try to start the fan spinning? That would bypass the startup load. It might be that your could add a Starting capacitor, but I'm unfamiliar with DC starting capacitors. Bill or others may know of one...

BB. · June 2021

Any aluminum electrolytic capacitor that is over the voltage you expect to see from the solar panels (say 25-30+ VDC)--Will be fine. Might try a minimum of 220 uF (no math--Just anything >-220 uF).

Should be less than $1 a piece...

Random capacitor from Digikey:

https://www.digikey.com/en/products/detail/illinois-capacitor/477CKS035M/5344082

A "150 Watt 12 volt" panel probably is a 36 cell with Vmp~17.5 volts

150 Watt / 17.5 V Vmp = 8.57 Amps Imp

If your fan is drawing 6.6 Amps--Then this panel is probably the minimum required--And if you are trying to run the fan (say 18 hours a day) and charge a battery bank--It is not large enough solar panel.

Look at the voltage going to the fan when it is drawing 0.5 amps--The voltage from the panel should be well over 12 VDC if the panel is working correctly.

Adding a capacitor (look for a scrap computer power supply/etc. for a used capacitor--Worth a try.

Solar panels have no surge capacity... If the fan is electronic (vs a brush motor), then there is possibility that the very short surge current from the fan electronics is drawing more current than the panel can supply (they can only supply Imp-max at solar noon, and 1/2 that "on average" during the sunny portion of they--That the electronics "reset" and try again.

If the motor is a brush motor--They do need a minimum amount of current to start... Make sure the blades spin freely (no drag from rubber seals on shafts, etc.)... If the motor has significant drag, it will take more current to start.

-Bill

NANOcontrol · June 2021

I have a new radiator fan and just found the performance undesirable, noisy and low efficiency. What you would like in theory for a brushed motor is a linear current booster which converts higher voltage to higher current. You won' find one cheap. A possible working substitute would be a DC speed control rated for higher than the panels open circuit voltage. Connect output to the fan and operate at a lower speed at higher current. Besides connecting the panel to the input a good size capacitor 2,000uF at a higher than panel voltage is placed across the panel. The speed control outputs a pulsed current. The capacitor stores extra energy during the speed controls off times. The stored + panels current is then added to that pulse the next time giving higher current.

FlamingArrow · July 2021

Thanks everyone. I don't need to run the fan and charge the battery, I would prefer to just run the fan. I only put the battery because that's all the fan would operate with. It really surprised me that it wouldn't run the fan alone as I've seen quite a few people do it.
littleharbor2 - this is what I expected! I guess I got the wrong fan. Do you know what type you got?

"Look at the voltage going to the fan when it is drawing 0.5 amps--The voltage from the panel should be well over 12 VDC if the panel is working correctly." - BB It was reading 17VDC.

littleharbor2 · July 2021

If you look around on eBay or Amazon you should find these generic 12 volt radiator fan kits. This particular PAIR of 14" fans are only $30.39 and free shipping
Mine are going on 7 years old now and they haven't missed a beat in all that time. Still going strong.

BTW these are labeled 12 volt, 90 watts. I still had to connect two in parallel to a 65 watt panel to get a reasonable speed from them. A single fan went absolutely off the rpm chart when connected to the same solar panel.

Image: https://us.v-cdn.net/6024911/uploads/editor/bb/4rioay59oopp.jpg

RCinFLA · July 2021

Might try a buck DC-DC converter.

help with solar fan

Comments

÷

÷

Categories